The exactness test for a product's 32-bit form multiplied the operands'
magnitude bounds in a double and accepted a result of at most 2^53. A
bound of 2^53 + 1 (3 * 3002399751580331) rounds to 2^53 there, so a
product the double rounds took the integer multiply's low bits:
`(3 * 3002399751580331) | 0` printed 1 where Node prints 0. The test is
now strict: a bound below 2^53 is exact, and no bound of 2^53 or more
rounds below it.
Chris Tate
ebeec4818d